Apparatus for contacting large volumes of gas and liquid across microscopic interfaces

ABSTRACT

An apparatus for contacting large volumes of gas and liquid together on a microscope scale for mass transfer or transport processes wherein the contact between liquid and gas occurs at the interfaces of a multitude of gas bubbles. Multiple porous tubes assembled in a bundle inside a pressure vessel terminate at each end in a tube sheet. A thin film helical liquid flow is introduced into the inside of each porous tube around and along its inside wall. Gas is sparged into the porous media and the liquid film so that an annular two phase flow with a uniform distribution of tiny gas bubbles results. The gas flow is segregated from the liquid flow without first passing through the porous media and through the liquid film. Nozzles at the lower end of the tubes divert liquid flow to a vessel and redirect the gas flow in a countercurrent direction.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority of U.S. Provisional Application Ser.No. 60/392,498, filed Jun. 28, 2002.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to apparatus and methods for creatingand maintaining controlled mass transfer, heat transfer, or chemicalreactions, and more particularly to an apparatus and method forcontacting industrial volumes of gas and liquid phases in closemicroscopic scale proximity with each other for the purpose of creatingand maintaining controlled mass transfer, heat transfer, or chemicalreaction to achieve a particular process.

2. Brief Description of the Prior Art

A wide variety of industrial operations depend on contacting a gas and aliquid together to achieve a process. These operations can generally becategorized by transport phenomenon where two (2) or more components ina system having a gradient will naturally equilibrate. Gradients occurin the system due to differing concentrations, temperatures, or simplyby differences in energy or motion between the components being broughtinto contact each with the other. Where the gradient is concentration,the transport is either by molecular mass transfer or convective masstransfer or both. In the cases where there are chemical interactionsbetween the components, the transport equilibria may or may not be overshadowed by the driving force of chemical equilibrium. In general, thesecomplex interactions which occur by contacting gas and liquid togethercan be categorized by the common terms mixing, stripping, evaporation,absorption, reaction, etc.

The literature dealing with mass transfer generally suggests thatmolecular mass transfer by diffusion plays a significant role even in afast moving system regardless of whether the system is chemicallyreactive or non-reactive. Diffusion occurs across spatially separatedcomponents due to a natural tendency to equilibrate. Depending on thesystem of interest, the process may be limited by the diffusivity or bytime. Diffusion may be vastly improved by minimizing the spatialdistance between components. Contacting large volumes of gas and liquidtogether in conventional equipment generally involves creating thelargest amount of liquid surface area by whatever means attainable in alimited volume. The result of this approach is most often a tall towercontaining either trays or packing material where the liquid is sprayedinto a gas phase or the gas is bubbled into the bulk liquid phase. Ineither case, the spatial separation between components is improved, butthe overall volume required to accomplish the contact conditions on acommercial scale can be quite large.

An obvious parameter necessary for either approach to tower design isthe acceleration of the components due to earth's gravity. Tower bubbletrays containing liquid rely on gravity to keep the liquid in the trays.Spray towers rely on gravity to accelerate liquid droplets downward. Itis clear that neither method would work well in the absence ofgravitational acceleration. For this reason and others, tower design istypically a large volume, low energy method for creating gas-liquidcontactors.

Miller, U.S. Pat. Nos. 4,279,743; 4,397,741; 4,399,027; and Miller etal, U.S. Pat. Nos. 4,744,890 and 4,838,434 disclose air spargedhydrocyclone apparatus (ASH unit) primarily for use as a type of airflotation device for removing particulate matter from a liquid.

Atwood, U.S. Pat. No. 4,997,549 discloses an apparatus and methodutilizing an air sparged hydrocyclone apparatus (ASH unit) forseparating hydrophilic particles from a fluid suspension containing bothhydrophilic and hydrophobic particles.

Grisham et al, U.S. Pat. Nos. 5,529,701; 5,531,904; 5,662,811;5,730,875, and 6,004,386 disclose a compact, high energy apparatus andmethod for contacting gas and liquid (the group of patents beinghereinafter referred to as the “Grisham, et al Patents”). The “Grisham,et al Patents” are based on accelerating a thin film of liquid in ahelical flow pattern around and along the inside walls of amicroscopically porous tube and sparging gas into the outside of thetube causing the gas to also pass through the thin liquid film. The goalcentral to these references is to decrease the diffusion distancebetween components by creating closely spaced gas bubbles in a fastmoving liquid so that gas-liquid interfaces are abundantly available formass transfer equilibrium to occur in a time as near instantaneously asis possible.

U.S. Pat. Nos. 5,529,701; 5,531,904; 5,662,811; 5,730,875, and6,004,386, (the “Grisham, et al Patents”), in which the inventor of thepresent invention was also a co-inventor, are hereby incorporated byreference to the same extent as if fully set forth herein.

Cairo, Jr. et al, U.S. Pat. No. 5,591,347 discloses a simplified singlecell apparatus and method for removal of suspended impurities in liquidsusing gas flotation and filtration. The method and apparatus arepreferably directed toward induced gas flotation separation of suspendedimpurities in combination with a filter media for filtration removal ofremaining suspended impurities. A filter media is contained within thesingle cell apparatus such that liquid exiting the vessel must passthrough the filter media after having been subjected to flotationtreatment.

A foreign treatise written on a compact, high intensity gas/liquidcontactor, “Stripping Performance of a New High Intensity Gas/LiquidContactor”, B. Waldie and W. K. Harris, Dept Mechanical and ChemicalEngineering, Heriot-Watt University, Edinburgh, UK exists in theliterature. A complete reference for this work is not known, but itappears to have been the culmination of a funded research supported bythe UK EPSRC and several oil operating companies as part of an MTDprogramme on “Treatment of Water Offshore-III”. This paper deals withthe comparative mass transfer performance of a laboratory device similarto both the Grisham, et al Patents” and ASH units and a small packedcolumn. The results given were for HTU or ‘Height of Transfer Unit’correlation whilst stripping toluene or oxygen from seawater and fromfresh water. The conclusion states a 250-fold improvement in processperformance of the compact device over a packed column.

In general, the prior art has taught a definite shift in thinking by theresearchers and developers working in this field. The shift isrecognition that liquid surface area can be increased by orders ofmagnitude over gravity dependent methods by containing liquid in anacceleration field and introducing gas into the acceleration field. Theintroduction of gas through porous media and further into the liquidprovides a convenient way to control the gas bubble size by choosingbeneficial porous media shape, porosity and permeability properties. Itis desirable to obtain the smallest practical gas bubble sizedistribution flowing through a thin liquid film to achieve the largestliquid surface area per unit volume. A flat porous plate with a fastmoving liquid film and introduction of gas from the underside of theplate would be a nice model to analyze mathematically, however, acylindrical porous containment is more practical to build and offersbetter control over liquid film thickness and fluid dynamics in general.The result of a radial acceleration field is that it is, for allpractical purposes, independent of its orientation with respect toearth's gravitational field.

The Grisham et al. patents teach a device that is generally horizontallydisposed relative to earth's gravitational field. The Grisham et al.patents also teach a device that comprises at least one cylindricalporous tube that is coaxially aligned with a non-porous outer jacket,more particularly, a long porous element divided into segregatedpressure chambers along the length of the porous tube. The porouselement may be divided into two or more segments and mated together endto end to form a longer tube. The acceleration stated to operate thedevice is up to 1500 times the earth's gravitational acceleration or32.2 ft/s² (g) or about 48,000 ft/s² or as little as 400 g or roughly13,000 ft/s². The stated volumetric gas rate to volumetric liquid rateis up to 50 to 1 or as little as 10 to 1. It is unclear whether thisvolumetric gas flow rate is based on standard temperature and pressureconditions or actual temperature and pressure conditions. Since gas iscompressible, the rates expressed in volumetric units can vary widelydepending on the temperature and pressure at actual conditions. Thestated number of liquid revolutions is up to 50 revolutions from thepoint of liquid introduction to the point of liquid exit from thedevice.

A great deal of effort and debate surrounds the length of porous mediarequired in this invention and consequently, the residence time requiredto achieve the desired results in a particular process. Grisham et al,U.S. Pat. No. 5,529,701, column 13, paragraph 25, suggests that eachincremental volume of liquid needs to reside for 0.5 seconds in the gassparged acceleration field to achieve equilibrium. With this timeparameter enforced in the design of the invention, it becomes more clearwhy the tube is so long, why the hydraulic energy and liquidacceleration is so large to move liquid to the end of a long tube, whythe volumetric gas rate is so high to balance the liquid energy withoutwetting the porous media over relatively large tube external surfacearea, and finally, why different gas pressure chambers are required toget good gas flow distribution along the entire length of a long poroustube. In practice, in those applications where diffusion distance limitsequilibrium, the time of contact is mostly irrelevant. In thoseapplications where chemical reaction time drives the process givenextremely short diffusion distances, the residence time has to beconsidered and consequently, the apparatus and method of operation mustallow adequate residence time to complete the specific reaction desired.Observation of test results with the Grisham et al. invention yieldssurprising results about the required residence time for a process tooccur. It is suggested here that the literature dealing with thissubject assumes a quiescent system where diffusion distance increasesthe time required to achieve equilibrium. In this system, the realresidence time required has yet to be discovered application byapplication and in every case appears to be less time than the bestprediction made by those observers skilled in the art of operating thesame process with conventional installed equipment. The porous tubeimplicated in the Grisham et al. invention is made excessively long byimposing a residence time parameter on the invention design and appliedto processes limited by diffusion distance and not by time. If thisparameter is relaxed based on empirical observation, the other operatingparameters and the overall invention design can be reworked, changed,and extended accordingly.

In practice, the Grisham et al apparatus has been manufactured usingstandard ‘off-the-shelf’ piping or tubing components such as tees andflanges. The device size is referenced by non-limiting example to flowbetween 15 and 250 gallons per minute of liquid. The device is scalableand it is stated in U.S. Pat. No. 6,004,386 at the top of column 16,“there may be a practical limit of scale versus utilization of multipleunits of apparatus to accommodate large flow rates.” Since the basis ofall Grisham et al. patents is for a “coaxially aligned cylindricalporous tube . . . and further including at least one nonporous outerjacket disposed concentric with said at least one porous tube . . . ”mated end to end, the scale-up to large process volumes wouldnecessitate a very large diameter porous tube. Although this may or maynot be physically possible to accomplish in practice, consider thefollowing example applied to the Grisham et al. design and utilizing thedesign parameters disclosed in the patents:

Assume process flow rate of 3000 gallons per minute,

Assume centrifugal acceleration=1000 g adequate to maintain liquid filmstability 1000 g=32,200 ft/s²=v²/r where v is velocity and r is poroustube radius,

A 20″ diameter porous tube is indicated based on area ratios of 1/3liquid, 2/3 gas.

Solving for velocity gives v=163.8 ft/s

The liquid injection nozzle cross-sectional area indicated is about 5.87sq. inches.

This example indicates a liquid flow nozzle having liquid velocity ofabout 164 ft/s, and a Reynolds Number for 60° F. water=2.6×10⁶.

The above example illustrates basic hydraulic principles, and referencesmay be found in the literature for the treatment of incompressibleviscous flow through pipes. Standard engineering practice normallyplaces a practical limit of flow velocity for liquids through pipes of15 ft/s and generally not to exceed 20 ft/s. Incompressible flow throughnozzles is generally discussed for flow metering devices in which theflow rate is proportional to the pressure drop measured across adiameter contraction. For meter applications, the calibration rangecited in numerous literature sources is limited to a Reynolds Number ofabout 1×10⁶. Although the nozzle is not a flow meter, the design basismay be similarly considered for practical application. If the designbasis of the nozzle is limited, and the limitation imposed is by theReynolds Number, then the limit for centrifugal acceleration in theabove example would become as follows:

Reynolds Number=1×10⁶

Velocity=62.7 ft/s

Centrifugal acceleration=393 ft/s²=12.2 g

Based on the recited parameters, 12.2 g would not be sufficient tooperate the device.

This example illustrates only one problem of scalability of the Grishamet al. apparatus. There are numerous others. The practical applicationof incompressible flow through the invention nozzle must also take intoaccount the presence of particulate material contained in the processliquid with some applications. Moving liquid at 164 ft/s where solidsare present in the liquid flowing through the invention nozzle wouldquickly erode the nozzle. The alternative method available to scale theGrisham et al. invention for large capacity is to utilize multipleapparatus assemblies of smaller capacity in place of one large capacityassembly. Since the invention is for a “coaxially aligned cylindricalporous tube . . . and further including at least one nonporous outerjacket disposed concentric with said at least one porous tube . . . ”,the use of multiple assemblies of the invention would take the form ofmultiple tubes with concentric tube outer jackets. For clarification,the form of the prior art applied to large flows requires using multipleassemblies of individual pressure containing units arranged in parallelto split a large process flow into numerous smaller flows fordistribution to each smaller invention assembly. This arrangement may ormay not be practical. The application of multiple pressure containinginvention assemblies may be driven by economics and not by engineeringdesign. The economics quickly reduce to an accounting of the number ofpipes, fittings, valves, meters, controls, and in general, all of theancillary equipment required to operate the invention arranged inindividual pressure containing assemblies for large capacity operationin an industrial setting.

The present invention is distinguished over the prior art in general,and these patents in particular by an apparatus and method forcontacting large volumes of gas and liquid together on a microscopicscale for mass transfer or other transport processes where the contactbetween liquid and gas occurs at the interfaces of a multitude of gasbubbles. The apparatus includes a plurality of cylindrical or conicalporous tube elements inside a pressure/vacuum vessel assembled in abundle similar to a heat exchanger and terminating at each end in a tubesheet; a tangential nozzle for introducing thin film liquid flow intothe inside diameter of each porous element in a helical flow patternaround and along the inside walls of the porous media; seals on each endof the porous media to segregate the gas flow from the liquid flowwithout first passing through the porous media and through the thinliquid film; an annular flow separator target nozzle at the second endof the porous section to divert liquid flow to a vessel and redirect thegas flow in a direction countercurrent to the liquid flow. The presentmethod of contacting large volumes of gas and liquid for mass transferor other transport processes in general comprises introducing a liquidflow tangentially into the inside diameter of each cylindrical orconical porous tube, assembled in a bundle and terminating at each endin a tube sheet, where the liquid flows in a thin film in a helicalpattern around and along the inside walls of the porous media,controlling the hydrodynamics of the flow; sparging gas into the porousmedia and the thin liquid film at a proportional flow rate to the liquidflow rate so that an annular two phase flow with a uniform distributionof tiny gas bubbles results; maintaining a pressure balance and adistinct boundary layer near the inside diameter of each tube where theporous media does not become wetted by the flowing liquid; maintainingthe annular thin film flow through the device so that enough energyremains to separate fluids due to differences in density at the exit ofthe device.

SUMMARY OF THE INVENTION

The present invention provides a method of creating and maintainingbeneficial physical conditions for the transport of momentum, heat, andmass between a liquid and a gas across a multitude of microscopicallysmall gas bubble interfaces so as to optimize the efficiency ofinterphase transport, and also provides economical modular apparatus foreffective industrial scale utilization of the method. With the methodand apparatus of the invention, interphase transfer equilibrium isachieved rapidly and within very compact theoretical unit volumes andphysical apparatus volume due to greatly reduced spatial separationbetween components allowing diffusion to occur almost instantaneously.

The apparatus of the present invention generally includes a bundle ofcylindrical or conical microscopically porous tubes, diametrically andcircumferentially evenly spaced inside a pressure/vacuum vessel,oriented where the centerlines of each tube are parallel to thecenterline of the vessel cylinder, terminating in perpendicular tubesheets similar to a shell and tube heat exchanger, sealed and seated atboth ends in tube sheet tube seats, open to flow at both ends in theinside diameter of each tube, with porous walls and hollow interiorscomprising each tube, liquid inlet nozzle assemblies disposed at thefirst ends of each tube, gas-liquid separator target nozzle assembliesdisposed at the opposite second ends of each tube, a liquid collectionpressure vessel, and a gas discharge assembly near the first ends of thetubes. The tubes are enclosed inside an outer vessel cylinder such thatit forms one or more chambers capable of being pressurized with gas. Thegas chamber may be commonly pressurized or it may be divided intomultiple chambers or sections so that one or more tubes or groups oftubes may be pressure isolated from the other tubes in the bundle anddistribution of gas to each tube or group of tubes may be controlledindividually. The liquid collection pressure vessel may be orientedeither vertically or horizontally depending on process requirements,preference and/or on the space available for a particular application.

Liquid is introduced tangentially into the inside diameter of each tubethrough liquid inlet nozzle assemblies with sufficient pressure and flowrate to create a high velocity flow of the liquid in a thin film aroundand along the inner surface of the porous wall of each tube. When theliquid meets the interior of a tube, the inlet velocity vector may ormay not be divided into a radial velocity component vector and alongitudinal velocity component vector. The longitudinal velocity vectorcomponent may at first introduction of liquid be equal to zero. Theaddition of a longitudinal velocity vector component, if desired, may beaccomplished by controlling the lead angle at which the liquid inletnozzle is disposed tangentially relative to the inside diameter of thetube. Where the direction of longitudinal flow in the device isapproximately in the same direction as earth's gravitationalacceleration vector, the lead angle is not particularly required toachieve the desired flow pattern. The high velocity flow of liquid in ahelical pattern around and along the inside walls of the tube produces acentrifugal or outward force of sufficient magnitude, acting to forcethe liquid against the inner surface of the tube with a velocity vectordirection generally normal or perpendicular to the longitudinal axis ofthe tube. The liquid radial velocity, and thus the outward acceleration,is sufficient to maintain the liquid film against the inner wall surfaceof the tube throughout its entire length.

In a first embodiment, pressurized liquid is introduced to all liquidinlet nozzle assemblies connected by a common pressure chamber at thesame flow rate and pressure simultaneously. In a second embodiment, eachinlet nozzle assembly has a separate liquid inlet and pressurized liquidis introduced to each porous tube individually. The liquid flow rate andpressure individually feeding each tube or group of tubes may becontrolled such that one or more tubes or group of tubes may be turnedoff while other tubes or tube groups are still in operation. Liquid flowcontrol in this configuration allows for sequential ranges or step-wiseturn-up/turn-down so that overall a broader range of process turn-downratio may be achieved. This arrangement also allows the use of tubes ofdiffering diameters and capacities to cover the overall liquid capacityrange and turndown ratio required by the process.

Pressurized gas is introduced into the pressure vessel chamber orchambers and forced through the porous walls of the tubes by virtue ofthe differential pressure between the pressurized gas chamber and theinside diameter zone of each porous tube. The tubes are seated andsealed in tube sheets such that the gas can only flow through the porouswalls of the tubes. Where liquid flow control exists for each tube orgroup of tubes individually in the bundle, the gas supply to the sameeach tube or group of tubes may be individually controlled so that gasis not flowing to a tube or tube group that is out of service. The gasexits the porous wall at its inside diameter surface and is immediatelycontacted by the liquid, which is moving at high velocity relative tothe tube wall and to the gas as it enters the interior of the tube. Thegas is sheared from the porous wall by a liquid boundary layer movingapproximately perpendicular relative to the gas. The result of thisintroduction of gas through the labyrinth of pores in the porous tubesinto a liquid having a centrifugal or outward acceleration in theapproximate opposite direction to the gas velocity vector direction isthat a multitude of very fine bubbles are produced, and are carried awayfrom the tube wall by the moving liquid in its radial flow patternaround the inside diameter surface of each porous wall, andlongitudinally toward the liquid exit from each tube. The mixture ofliquid and gas bubbles forms a two-phase flow that exists in a helicalflow pattern around and along the inner surface of each tube. Thebuoyancy of the bubbles relative to the liquid causes them to movetoward the region of lowest pressure or the center zone of the tube andagainst the centrifugal (outward) acceleration of the liquid phase,passing through the froth created by the two phase flow as it movesaround the inner surface of each tube. The gas exits from the two-phaseflow at the inner flow boundary created at the inside diameter of thethin film and is transported axially from the tube. Because the specificgravity of the liquid is much higher than the specific gravity of thegas, the centrifugal acceleration imposes a substantially higher forceon the liquid than on the gas. The gas is thus able to move to thecenter of the tube while the liquid is forced toward the wall of thetube. The result of this density difference produces a distinct gasphase in and along the axial core of each porous tube, minimizing liquidentrainment with the gas in the central portion of the tube, andinducing a clean separation between the gas column at the center of thetube and the two phase flow along the inside diameter surface of thetube.

As the bubbles pass through the liquid, momentum, heat and mass aretransferred on a molecular level between the liquid and the gas inaccordance with the laws of thermodynamic equilibrium. Mass transferoccurs between the two components as determined by the value of theappropriate partition coefficient and the initial concentration of thetransferring component in each phase. In general, the concentrations ofthe transferring component in each bubble of gas and in the immediatelysurrounding liquid are at or closely approaching equilibrium when thegas in each bubble exits from the liquid to the gas column at the centerof the tube. Each volume of gas passes through the liquid only oncewithin the apparatus, and each passage is associated with an approach toequilibrium.

The modular configuration of the present invention allows parameters tobe adjusted for the most efficient operability range including broadturn-up/turn-down ratios that invariably have to be considered andincorporated. The modularity of the present invention also allowsreduction of studies in process design, mechanical design, and costaccounting to determine the initial best tube diameter/length ratioversus tube number to roughly size for the operability range of theprocess. The process performance may be fine-tuned by simply adding orsubtracting a tube from service. Tube porosity and tube length, liquidfilm thickness, gas outlet nozzle diameter, etc. can each be changed outin total or in selected contactors in the bundle.

Consolidating the gas-liquid contactor and associated hardware needed tohouse the porous tubes, collect liquid, scrub gas, etc. into apressure/vacuum vessel allows further use of conventional vesselinternal devices like baffles, mist eliminators, vanes, vortex breakers,etc. to improve the overall performance of the present invention. Forexample: gas baffles in the gas supply section of the vessel to preventthe incoming gas stream from impinging directly on the outside surfaceof a porous element and potentially creating uneven gas distribution tothe entire available external surface area of the cylindrical or conicalelement; liquid motion baffles to mitigate sloshing for those processapplications where the vessel is mounted on and operates on a movingdeck, mesh pads and/or vane packs used in the gas scrubber section ofthe vessel to minimize any entrained liquid carryover prior to the finalgas exit from the invention. Vessel external hardware commonly requiredto fabricate, install, start, and safely operate the process, and/orrequired by code may also be incorporated and would appear as vesselnozzles for level gauges/transmitters, extra vessel nozzles in generalneeded for gauges, meters, switches, vents/drains, pressure safetyvalves, etc.; along with required manways, davits, lifting lugs, codestamps, nameplates, etc.

The apparatus and method of the present invention, as well as thefeatures and advantages associated therewith, will be described in moredetail with reference to the accompanying drawing figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic longitudinal cross-section of a first embodimentof the apparatus of the present invention, showing the major assembliesand functional zones of operation.

FIG. 2 is a schematic longitudinal cross-section of the first embodimentof the first embodiment with reference numerals identifying the partsand regions of the invention.

FIG. 3 is a schematic longitudinal cross-section of a second embodimentof the apparatus, showing the major assemblies and functional zones ofoperation.

FIG. 4 is a schematic longitudinal cross-section view of the secondembodiment with reference numerals identifying the parts and regions ofthe invention.

FIG. 5 is an enlarged longitudinal cross-section view showing thedetails of a preferred embodiment of a porous tube cartridge.

FIG. 6 is a transverse cross-section view through the gas-liquidcontactor section, showing the multiple porous tubes arranged in abundle.

FIG. 7 is an enlarged transverse cross-section view of a porous tubeshowing, schematically, the features of liquid film and gas bubblespresent when the apparatus is in operation.

FIG. 8 is an enlarged longitudinal cross-section view of the liquid feedand gas exhaust section and the liquid inlet nozzle assemblies of thefirst embodiment of the invention.

FIG. 9 is an enlarged longitudinal cross-section view of a firstembodiment of the liquid exit section and liquid separator nozzleassembly that may be used in the first or second embodiments of theapparatus.

FIG. 9A is an enlarged longitudinal cross-section view of an alternateembodiment of the liquid exit section and a conical liquid separatornozzle assembly that may be used in the first or second embodiments ofthe apparatus.

FIGS. 10A and 10B are a partial longitudinal cross-section view and topplan view, respectively, of the liquid inlet nozzle housing of the firstembodiment of the invention.

FIGS. 11A and 11B are a partial longitudinal cross-section view and atop plan view, respectively, of the liner member of the liquid inletnozzle assembly.

FIGS. 12A and 12B are a longitudinal cross-section view and a top planview, respectively, of the vortex finder member of the liquid inletnozzle assembly.

FIGS. 13A and 13B are a partial longitudinal cross-section view and topplan view, respectively, of the liquid inlet nozzle housing of thesecond embodiment of the invention.

FIG. 13C is a longitudinal cross section view of one of the replaceablenozzle inserts of the liquid inlet nozzle assembly of the secondembodiment.

FIG. 14 is a schematic view similar to FIG. 2 with added piping for gaspressure equalization between the liquid collection vessel and the gasdome and several additional components in various sections.

FIG. 15 is a schematic longitudinal cross-sectional view of the firstembodiment of the apparatus showing, schematically, an assembly havinglongitudinally segregated gas-liquid contactor sections.

FIGS. 16A and 16B are schematic diagrams showing arrangements wherein apair of the gas-liquid contactor assemblies are operated in series andin parallel, respectively.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following discussion, the apparatus for contacting large volumesof gas and liquid across a multitude of microscopic interfaces of theinvention will be described in detail, followed by a description of themethod of operation. Referring to the drawing figures, a firstembodiment of the invention is shown, somewhat schematically, in crosssection in FIGS. 1 and 2, and a second embodiment is shown in FIGS. 3and 4, which differs from the first embodiment in the uppermost section.Both embodiments have a gas-liquid contactor section 100, a liquid exitsection 300 below the gas-liquid contactor section, and a liquidcollector section 400 below the liquid exit section. The firstembodiment of FIGS. 1 and 2 has a liquid feed and gas exhaust section200 above the liquid contactor section and a gas dome 500 above theliquid feed section, whereas the second embodiment of FIGS. 3 and 4 hasa different type of liquid feed and gas exhaust section 600 and no gasdome. The features of sections 100, 300 and 400 are essentially the samein each embodiment of the invention.

The gas-liquid contactor section 100 comprises an outer vessel 101having a central longitudinal axis circumscribed by a non-porousgenerally cylindrical side wall 102 with an upper flange 103 and a lowerflange 104. Referring additionally to FIGS. 5, 6, 7, 8 and 9, aplurality of elongate tubes 105 are disposed within the outer vessel 101in circumferential and radially spaced relation with their longitudinalaxes parallel to the outer vessel longitudinal axis. Each of the tubes105 has a microscopically porous side wall 106 with an inner surfacesurrounding a hollow interior 107 and opposed first (upper) and second(lower) ends 108 and 109, which are non-porous and provided with sealmeans 110, such as an O-ring seal. The tube ends 108 and 109 may bewelded, glued, cast, molded, fused, or otherwise formed or attached tothe porous tube 105 so that the tube can be sealed at both ends, and beeasily replaceable. The cross-section of the porous tubes 105 may becylindrical or conical. As best seen in FIGS. 8 and 9, the exterior ofeach of the first (upper) ends 108 of the tubes 105 is sealingly engagedin a respective bore 112 in a first disk-shaped tube sheet 111 bolted tothe upper flange 103 of the outer vessel 101 and the exterior of theirsecond ends 109 are sealingly engaged in a respective bore 114 in asecond disk-shaped tube sheet 113 in the outer vessel having an outerperiphery engaged in sealing relation with the interior surface of theouter vessel side wall 102, similar to a shell and tube heat exchanger.Thus, the tube sheets 111 and 113 form a pressurized gas chamber 115surrounding the tubes 105 in upper portion of the outer vessel (FIGS. 2and 4) and the second tube sheet 113 forms a gas-liquid separatorchamber 116 isolated therefrom in the lower portion of the outer vessel,and the interior of the tubes are open to liquid flow through the tubesheets. The outer vessel 101 has at least one gas inlet 117 with aninterior in fluid communication with the gas chamber 115 forpressurizing it with gas.

In the first embodiment of FIG. 2, there is a single gas chamber 115 andin the second embodiment of FIG. 4, the gas chamber 115 is partitionedby plates 118 into multiple segregated pressurized gas chambers eachhaving a respective gas inlet 117, so that one or more tubes 105 orgroups of tubes may be pressure isolated from the other tubes in thebundle and distribution of gas to each tube or group of tubes may becontrolled individually.

The porous tubes 105 may be in the form of cartridges and may be made ofany compatible material having suitable properties of geometry, porosityand permeability, corrosion resistance, thermal stability, etc. Theporosity range of interest used is generally about 0.5 micron up to 40microns.

The materials of construction of porous tubular elements is widelyavailable in plastics such as Kynar™, Teflon™, polypropylene, etc.; inmany metal alloys such as 316 stainless steel, nickel-aluminum-bronze,nickel alloys—Hastelloy™, Monel™, etc., tantalum, etc.; and in ceramicmaterials—aluminas, cordierites, silicon carbide, aluminum nitrides,zirconias and/or composite ceramic structures. The media may also becomposites of laminated materials designed to produce the desiredcombination of properties. Porous media produced by other methods ofmanufacture, such as woven wire mesh, may also be used. In general, anyporous media, regardless of material or manufacturing approach, may beused, so long as the media is capable of suitable performance under theconditions to which it will be exposed. In some applications, surfaceactive catalytic materials may be embedded or otherwise be present inthe porous media. The surface finish on the inside diameter of thetubular elements may be further treated to enhance liquid flowproperties. An example surface treatment used with some metal alloyporous tubes is electropolishing. In some cases, the tubes may bereconditioned and reused by cleaning methods like ultrasonic bath,solvent wash, heating or combination thereof to restore the tubepermeability to the near new condition. ASTM (American Society forTesting Materials) and ISO (International Organization forStandardization) both have published standards for permeabilitymeasurement technique generally involving a bubble point test. Bubblepoint testing may be used to generate a baseline performance for theporous tube cartridges and further used to re-certify a reconditionedtube.

One of the main features of using porous tubes 105 to produce amultitude of tiny bubbles in a liquid stream is the ability to supplyclean gas to the apparatus. The porous media is not intended to providegas filtration. It should be understood that polishing filters, whererequired, may be used upstream of and/or around each porous element 105inside the gas supply chamber 115 to provide the final polishingfiltration for the gas. In some cases, additional gas pretreatment maybe required to remove particulate matter and/or remove condensableliquids prior to introduction into the apparatus.

Referring now to FIGS. 8, 10A, 10B, 11A, 11B, 12A and 12B, the liquidfeed and gas exhaust section 200 of the first embodiment is shown ingreater detail. A liquid inlet and gas exhaust nozzle assembly 119 issecured over each of the bores 112 in the first tube sheet 111 in axialalignment with the bores and the first or upper end 108 of each tube105. The liquid inlet and gas exhaust nozzle assembly 119 includes anozzle housing 120 (FIGS. 10A, 10B) having a generally cylindrical sidewall 121 with a radial flange 122 at its bottom end, a larger interiordiameter 123 extending upwardly therefrom, a reduced diameter exhaustopening 124 at its top end, and a rectangular liquid inlet nozzleaperture 125 through its side wall tangential to its interior diameterto establish tangential liquid flow of a thin film of incoming liquid.The rectangular nozzle aperture 125 is precisely formed by removingmaterial on the side wall 121 of the nozzle housing to establish liquidcommunication with a nozzle line 126 (FIGS. 11A, 11B). The nozzle liner126 is a hollow cylindrical member having a side wall 127 surrounding aninterior diameter 128 and an outer diameter 129 that fits preciselyinside the interior diameter 123 of the nozzle housing 120 so that thetolerance or fit-up of the liner outer diameter is as close as possiblewithout interference between the two parts. The nozzle liner 126 has arectangular liquid inlet aperture 130 formed in its side wall tointroduce liquid flow in a thin film 156 (shown schematically in FIG. 7)disposed tangentially to its inside diameter 128 and dimensioned to lineup with the liquid inlet aperture 125 of the nozzle housing 120. Theliquid inlet aperture 130 has a cross sectional area to produce a thinfilm of liquid having a thickness in the range of from about 5% to about28% of the inside diameter of the tube. The liner 126 is pinned at 131to the tube sheet 111 or otherwise prevented from rotating out ofalignment when pressurized liquid is forced at a high velocity throughthe aperture 130. The inside diameter 128 of the liner 126 and theinside diameter 107 of the porous tube 105 are approximately the samediameter so that the thin film liquid flow is not disturbed as in passesalong the transition between the liner 126, the tube sheet bore 112, andon into the porous tube. The nozzle liner 126 may be made of ceramicmaterials and be easily replaced periodically in those applicationshaving very high fluid velocities and/or erosive solids in the liquid.

A vortex finder 132 (FIGS. 12A, 12B) is disposed within the nozzlehousing 120. The vortex finder 132 is a generally cylindrical memberhaving a reduced diameter lower portion 133 and a larger diameter upperportion 134 defining a radial shoulder 135 therebetween that rests onthe top end of the liner 126. The upper portion 134 is provided withseal means 136, such as an O-ring in an O-ring groove, which engages theinterior diameter 123 of the nozzle housing 120 in a fluid tight sealingrelation and the reduced diameter lower portion 133 is radially spacedfrom the interior diameter 128 of the liner 126, defining an annulus 141therebetween (FIG. 8). The vortex finder 132 has a central bore 137coaxial with the exhaust opening 124 in the nozzle housing 120 and aninterior conical diverging lower portion 138 to provide a flow path forexhausting return gas into the gas dome 500 (described hereinafter). Thecentral bore 137 of the vortex finder 132 is the converging-diverginggas exit nozzle throat passage that allows processed gas to exit fromthe gas-liquid contactor section 100 into the gas dome 500. Thus, thevortex finder 132 establishes vortex flow of incoming liquid, andprovides a physical separation between the incoming liquid and exhaustedreturn gas.

In applications at, or approaching, sonic gas velocity, the central bore137 is the limiting diameter to determine how much gas at a particularpressure and temperature can be moved through the nozzle assembly. Thecentral bore 137 and conical diverging lower portion 138 may be enlargedto accommodate higher flows and may be used in conjunction with conicaltubes to accomplish the desired diameter and subsequent flow rate at apredetermined pressure drop through the apparatus. The reduced diameterlower portion 133 of the vortex finder 132 is approximately the samediameter as the inner diameter of the liquid film 156 (shownschematically in FIG. 7) before introduction of gas into the liquid thatcauses the liquid film to thicken slightly.

The liquid inlet nozzle assembly 119 is bolted, or otherwise fastened,onto the tube sheet 111 by bolts 139 passing through bolt holes in theradial flange 122 of the nozzle housing 120 and threadedly engaged inthreaded holes in the tube sheet. Seal means 140, such as an O-ring inan O-ring groove is provided on the side wall of the nozzle housing 120near its top end.

In the first embodiment of FIGS. 1 and 2, a gas dome 500 is mountedabove the liquid feed and gas exhaust section 200. The gas dome 500 is agenerally dome shaped vessel having cylindrical side wall 142 with anupper and lower radial flange 143 and 144 at its top and bottom end,respectively. As best seen in FIG. 8, the lower radial flange 144 isbolted in sealing relation onto the tube sheet 111 by bolts passingthrough bolt holes in tube sheet and in the upper flange 103 of theouter vessel 101. A dome-shaped end member 145 has a radial flange 146that is bolted in sealing relation to the upper radial flange 143. Theinterior of the gas dome 500 is divided by a divider plate or tube sheet147 into a separate liquid chamber 148 at its lower end and a gasexhaust chamber 149 above the tube sheet which serves as a gas scrubbersection. The dome-shaped end member 145 has a gas outlet 150 with aninterior in fluid communication with the gas exhaust chamber 149. Asseen in FIG. 8, the divider plate or tube sheet 147 has a central bore151 and a plurality of circumferentially spaced gas exhaust bores 152extending therethrough in radially spaced relation thereto. The seals140 on the side wall of the nozzle housings 120 are sealingly engaged incounterbores on the bottom end of the gas exhaust bores 152 to form aliquid and gas tight pressure containing seal between the liquid chamber148 and the gas exhaust chamber 149 to prevent incoming liquid fromescaping into the gas exhaust chamber. The seal means 136 on the upperportion 134 of the vortex finder 132 prevents incoming high pressureliquid from escaping from the nozzle housing 120 into the gas exhaustchamber 149.

A liquid inlet conduit or pipe 153 having an outer end external to thegas dome 500 extends in sealed relation through the gas exhaust chamberside wall 142 and has a second end sealingly engaged in the central bore151 of the divider plate or tube sheet 147. The interior 154 of theliquid inlet pipe 153 is in fluid communication the liquid chamber 148,which surrounds the nozzle assemblies 119. The outer end of the inletpipe 153 may be flanged. Thus, in the first embodiment, liquid isintroduced into the liquid chamber 148 through the inlet pipe 153 andfed simultaneously to all of the liquid inlet nozzle apertures 125 inthe side wall of the nozzle housings 120, and into the tangentialaperture 130 of the liners 126 and is trapped by the vortex finders 132so that liquid can only flow in one direction in a helical flow patternaround the liners 126, through bores 112 in tube sheet 111, into thetube ends 108, and further into the inside diameter of the porous tubes105 (shown schematically in FIG. 7). The flow pathway created throughthe mated parts described above produces a smooth, continuous flow ofliquid in a pattern similar in appearance to the rifling marks inside agun barrel. Angular or radial misalignment of the flow pathway producesundesirable flow disturbances and is amplified with increasing liquidvelocity.

In the following discussion of the second embodiment, the componentsthat were shown and described in detail previously with reference to thefirst embodiment are assigned the same numerals of reference, but theywill not be described in detail again here to avoid repetition.

Referring now to FIGS. 3, 4, 13A, 13B and 13C, in the second embodiment,the gas chamber 115 of the outer housing 101 is partitioned by plates118 into multiple segregated pressurized gas chambers each having arespective gas inlet 117, so that one or more tubes 105 or groups oftubes may be pressure isolated from the other tubes in the bundle anddistribution of gas to each tube or group of tubes may be controlledindividually. The second embodiment also has a different type of liquidinlet nozzle assembly 161 in the liquid feed and gas exhaust section600, which is disposed at the first or upper end 108 of each tube 105,and is not enclosed by a dome section. As shown in FIGS. 3 and 4, adisk-shaped tube sheet 162 is bolted to the upper flange 103 of theouter vessel 101. The exterior of each of the first (upper) ends 108 ofthe tubes 105 is sealingly engaged in a respective bore 163 in the tubesheet 162. Thus, in this embodiment, the liquid inlet nozzle assembly161 is external to outer vessel 101 and also forms the pressurecontaining gas exhaust piping that allows gas to exit the apparatus.

As shown in FIGS. 13A and 13B, each of the nozzle housings 164 of thesecond embodiment is a generally cylindrical member having a radialflange 165 at its bottom end with bolt holes in a pattern matchingthreaded holes in the tube sheet 162, a larger interior diameter 166extending upwardly therefrom with a reduced diameter exhaust opening 167at its top end in communication with the interior 169 of an elongateexhaust outlet 168 having a radial flange 170 at its outer end throughwhich gas is exhausted. A liquid inlet 171 extends outwardly from theside of the nozzle housing 164 and, as shown here, has a Victaulic-typecoupling groove 172 near its outer end, but not limited thereto. Theinterior of the liquid inlet 171 has a central bore which receives apair of replaceable nozzle inserts 173 and 174 held in place by aretainer 175. The insert 173 is cylindrical. As best seen in FIG. 13C,the insert 174 has a curved end 174A matching a curved segment of theinterior diameter 166 of the nozzle housing 164, and a rectangular inletaperture 176 configured to establish fluid flow of a thin film ofincoming liquid tangential to the side wall of the interior diameter ofthe nozzle liner 126, as described below. The nozzle inserts 173 and 174may be made of ceramic materials and be easily replaced periodically inapplications having very high fluid velocities and/or erosive solids inthe liquid.

The same vortex finder 132 (FIGS. 12A and 12B) and nozzle liner 126(FIGS. 11A and 11B) described previously above are installed in theinterior diameter 166 of each nozzle housing 164. Liquid enteringthrough the inlet 172, passes through the insert 173, the rectangularinlet aperture 176 of insert 174, into the rectangular inlet aperture130 of the nozzle liner 126, and is trapped by the vortex finder 132 sothat liquid can only flow in one direction in a helical flow patternaround the liner 126, through bore 163 in tube sheet 162, into the tubeend 108, and further into the porous tube 105.

Referring now to FIGS. 1, 2, 3, 4 and 9, the gas-liquid contactorsection 100 of the vessel functions to bring large volumes of gas andliquid into microscopically close contact each with the other, and thegas-liquid separator section 300 (FIG. 9) of both embodiments functionsto subsequently separate gas and liquid constituents back apart fromeach other after having been in contact and after having transferredmass, heat and/or momentum to the extent that thermodynamic and/orchemical equilibrium dictates. The gas-liquid separator section 300terminates at its lower end with the lower flange 104 of the outerhousing 101, which is connected to a flange 178 at the top end of thepressure vessel 177 that serves as the liquid collector section 400 ofthe apparatus.

As best seen in FIG. 9, the second tube sheet 113 at the lower ends 109of the tubes 105 forms a part of a gas-liquid separator nozzle assembly.The tube sheet 113 has machined bores 114 that form tube seats for thelower ends 109 of the tubes 105 to both seal and terminate and alsoprovide a continuing path for the helical thin film liquid flow to exitthe gas sparged contactor section 100 of the apparatus. The tube sheetbores 114 may be cylindrical or may be tapered, as shown, and asrequired to accelerate the liquid slightly and serve as a convergingnozzle throat to provide a smooth transition zone wherein the 2-phaseflow has time to degas and separate as cleanly as possible into a liquidstream and a gas stream (described hereinafter). The length of thedegassing zone is arbitrarily chosen in this embodiment as about 8 to 10liquid film thicknesses or stated another way, about one tube diameter.

Solid target nozzles 179 at the upper end of longitudinal tubularcomponents 180 and 181 are secured in permanent precise positionconcentrically and axially partially in the bores 114 by supports 182.The design and positioning of target nozzles 179 relative to theconverging bore 114 forms an annular gas-liquid separator annulus 183that allows liquid to pass through and redirects gas in a directioncountercurrent to the direction of liquid flow in the contactor section100 above it. The shape, size and positioning of the target nozzles 179relative to the converging bores 114 determines the gas-liquid separatorefficiency. In the illustrated embodiment, the target nozzles 179 areshown as a simple conical shape, which testing has shown to workeffectively. The diameter of the target nozzle 179 is approximatelyequal to the tube inside diameter minus two liquid film thicknesses. Thenozzle as shown does not separate 100% of each distinct phase cleanlyand passes a small fraction of gas along with the liquid flowing out ofthe annulus 183. This inefficiency may be overcome by the addition ofgas pressure equalization piping 184 connected in fluid communicationbetween the interior 149 of the gas dome 500 and interior 185 of theliquid collection vessel 177 as shown in FIG. 14 and describedhereinafter.

The nozzle supports 182 may be an assembly of round bars or flat barsarranged in a grid, or may take the form of perforated plates where anadditional benefit may be derived using the supports additionally asperforated baffle plates to discourage foaming of certain liquids asrequired for certain processes. Examples of foaming liquids that may beprocessed with the invention are seawater, crude oil, or any liquidcontaining surfactants.

The design of the gas-liquid separator section 300 of the apparatus hasbeen determined largely from experimental testing. Two main featuresshould be emphasized here. The contactor section 100 of the apparatus isvery sensitive to backpressure and a trade-off exists between gas-liquidseparator efficiency and backpressure on the unit. For example, theannulus 183 around the nozzle 179 could be reduced to a dimension lessthan the liquid film thickness so that only liquid passes through. Bydoing this, the liquid backs up into the thin film flow and causes theliquid film thickness to expand where, in the limiting case, the poroustubes 105 could become completely flooded with liquid. Thus, it isimportant to allow generous annular space for liquid to exit the nozzleso that the tubes are never completely flooded with liquid under anysteady operating condition. The second feature involved with a slightlyinefficient gas-liquid separator nozzle is the desire to limit furthercontact between the gas and liquid after exiting the contactor sectionof the vessel. Although the gas at the center 107 of the tubes 105 andthe liquid 156 (FIG. 7), as a component of the two phase flow, are indirect contact at the interface 157 created between the central gascolumn 107 and the annular liquid-gas boundary 157, moving in alongitudinal direction countercurrent to each other, the physicaldynamics of the system effectively minimize the possibility of remixing.The area of interfacial contact between the gas at the center 107 of thetubes 105 and the liquid in the two phase flow along boundary 157,across which mass transport might occur, is insignificant in comparisonto the area of interfacial contact between the gas bubbles 159 movingthrough the liquid 156 to the center 107 of the tubes 105. If, however,too much inefficiency exists in the gas-liquid separator, thenpartitioning between the gas and liquid can reverse a fraction of themass transfer just completed in the contactor section as the flow movesinto the vessel 177 of the liquid collector section 400. It is desirableto arrive at the best design compromise that does not place backpressureon the unit and minimizes the volume of gas escaping with the liquid outof the annulus 183. The annular gas-liquid separator may be furtherimproved by the addition of vanes or other fluid flow control deviceswhether rotating or non-rotating that serve to improve the efficiency ofseparation without increasing the backpressure on the contactor section.

As shown schematically in FIG. 14, another feature of the target nozzleof the present invention is that the solid portion 179 of the targetnozzle may be used to house a small measurement or monitoring device 201such as a camera or opacity monitor, or to provide a mechanical supportand electrical termination point for other electronic or electricaldevices 202, such as resistance heating elements or ultraviolet emittinglight sources in the interior 107 of the tubes 105.

FIG. 9A shows an alternate embodiment of a conical gas-liquid separator186. The inefficiency of separation, discussed above, may be improved byusing a conical or apex nozzle 187 attached to the bottom of tube sheet113. The apex nozzle 187 provides a simple combination degassingtransition zone and gas ‘valve’ in one flow control shape. The liquidaccelerates as it is forced into a converging diameter 188 therebyimproving degassing of the liquid. The apex nozzle angle and dischargediameter 189 are carefully chosen to minimize backpressure on the liquidwhile simultaneously minimizing the amount of gas that can pass throughthe nozzle. The gas runs into the liquid leading into diameter 189 anddue to a very slight pressure build-up, exits in the reverse orcountercurrent direction to a zone of lower pressure. One of the mainfeatures of the alternate embodiment is its simplicity, the reduceddifficulty encountered in the fit-up required to precisely locate anannular target nozzle, and in the added benefit of reducing thethickness of material required to manufacture tube sheet 113.

Certain applications of the apparatus are not adversely affected bycompletely removing a precision gas-liquid separator nozzle at thetermination of the sparging zone. In those cases, tube sheet 113 may beused “as-is” without any further attachments or modification to providetube seats and a transition zone for the ceasing of gas sparging. Inthis case, the gas may travel axially in both the co-current andcountercurrent directions inside tubes 105 and further may be evacuatedfrom both the upper region of the liquid collection vessel 177 and theexhaust outlet 150 at the top of the gas dome 500.

The liquid collection vessel 177 (FIGS. 2 and 4) that serves as theliquid collector section 400 of the apparatus is a pressure vesselhaving a flange 178 at its top end connected to the lower flange 104 ofthe gas-liquid separator section 300 and an interior 185 in fluidcommunication with the gas-liquid separator chamber 116 beneath thesecond tube sheet 113 and with the lower ends 109 of the porous tubes105 through the annulus 183 between the target nozzle 179 and the bores114 in the tube sheet to receive liquid passing through the annulus. Thevessel 177 has a liquid outlet 190 at its bottom end for removing liquidcollected therein. The vessel 177 may be manufactured from standardpressure vessel materials and, if necessary, further protected fromcorrosive service applications by using liner materials or coatings onthe inside of the vessel. Certain processes are optimally operated undervacuum. In those cases, the vessel must be designed accordingly towithstand external pressure instead of internal pressure.

Preferably, the governing pressure design basis and the fabricationmethod and inspection criteria used to construct, test, and operate thepresent apparatus is in accordance with the American Society ofMechanical Engineers (ASME) Boiler and Pressure Vessel Code (B&PV)Section VIII Division 1 or 2 and/or ANSI/ASME B31.3 Process Piping Codefor piping attachments to the vessel.

It should be understood that conventional external vessel hardwarecommonly required to fabricate, install, start, and safely operate theprocess, and/or required by code may also be incorporated. Theseadditional attachments are typically vessel nozzles for levelgauges/transmitters, extra vessel nozzles in general needed for gauges,meters, switches, vents/drains, pressure safety valves, etc.; along withrequired manways, davits, lifting lugs, code stamps, nameplates, etc.

The modular tube bundle packaging approach of the present inventionallows for several additional features to be incorporated. Consolidatingthe gas-liquid contactor and associated hardware needed to house theporous tubes, collect liquid, scrub gas, etc. into a pressure/vacuumvessel allows further use of vessel internal devices like baffles, misteliminators, vanes, vortex breakers, etc. to improve the overallefficiency of the invention.

For example, as shown schematically in FIG. 14, gas baffles 203 may beprovided in the gas supply chamber 115 of the outer housing 101 toprevent the incoming gas stream from impinging directly on the outsidesurface of a porous element 105 and potentially creating uneven gasdistribution to the entire available external surface area of theelement. Liquid motion baffles 204 may be provided in the interior 185of the liquid collection vessel 177 for those process applications wherethe vessel is mounted on and operates on a moving deck. Gas pressureequalization piping 184 connected in fluid communication between theinterior 149 of the gas scrubber section of the gas dome 500 and theinterior 185 of the liquid collection vessel 177 may be required in someinstallations to equalize the pressure between the first ends 108 andthe second ends 109 of the porous tube elements 105. As discussed above,the gas-liquid contactor is very sensitive to built-up backpressure. Theaddition of pressure equalization piping 184 prevents built-upbackpressure from occurring in the vessel 177. Mesh pads and/or vanepacks 205 may be used in the gas scrubber section 149 of the gas dome500 and/or at the ends of the gas pressure equalization piping 184 tominimize any entrained liquid carryover prior to the final gas exit 150from the apparatus. The gas dome 500 provides some gas scrubbing actionwithout the use of additional mist elimination devices by virtue of thedecrease in gas velocity as it exits bores 137 of the vortex finders 132and into the larger volume of the interior 149 of the gas dome 500. Theaccumulation of liquid in the gas scrubber section 149 of the gas dome500 may be automatically drained to the vessel 177 through pipingattachment 209. Heating elements 206 or a heat exchanger may be providedin vessel 177 to add heat or preheat exchange to the process. Heated gasor heated tubes may be used in some applications to prevent condensableliquids from condensing inside the porous wall of the media due to thepressure drop experienced while flowing through the porous media and/orthin liquid film. For example, the porous media of the tubes 105 may beconnected to an electrical source 207 and electrified to additionallyserve as a resistance heating element. Polishing filters 208 may be usedupstream and/or around each porous element 105 inside the gas supplychamber 115 to provide final polishing filtration for the gas.

The modular, bolt together configuration of the apparatus isparticularly well suited for utilizing multiple combinations ofcomponents. For example, FIG. 15 shows schematically, an assemblywherein an intermediate or second gas-liquid contactor section 100Ahaving an outer housing 101A with upper and lower flanges 103A and 104Ais bolted between the outer housing 101 of the first gas-liquidcontactor section 100 and the gas dome 500, described above. A pluralityof elongate tubes 105A are disposed within the outer vessel 101A andsealingly engaged at their first ends in a respective bore in a firsttube sheet 111 bolted between the upper flange 103A of the outer vessel101A and the flange 144 of the gas dome 500 and their second ends aresealingly engaged in a respective bore in an intermediate tube sheet113A bolted between the lower flange 104A of the housing 101A and theupper flange 103 of the first vessel 101. Thus, the tube sheets 111,113A and 113 form a first pressurized gas chamber 115 surrounding thetubes 105 in upper portion of the first vessel 101 and a secondpressurized gas chamber 115A surrounding the tubes 105A in the secondvessel 101A separated therefrom by the tube sheet 113A, and the secondtube sheet 113 forms a gas-liquid separator chamber 116 in the lowerportion of the first vessel. The interior of the tubes 105A and 105 areaxially and radially aligned and open to liquid flow through the tubesheets such that a smooth flow pattern results. Each outer vesselsection 101 and 101A has at least one gas inlet 117, 117A with aninterior in fluid communication with the respective gas chambers 115 and115A for pressurizing it with gas. In a longitudinally stacked contactorconfiguration of the second embodiment of the invention, either of thegas chambers may be partitioned by plates into multiple segregatedpressurized gas chambers each having a respective gas inlet, so that oneor more tubes or groups of tubes may be pressure isolated from the othertubes in the bundle and distribution of gas to each tube or group oftubes may be controlled individually.

In this arrangement, the porous tubes 105 and 105A may be selected anddimensioned to provide sufficient tube surface area for the particularapplication. The tubes or groups of tubes 105, 105A may be selected toisolate pressure along the length of the porous media to achieve uniformgas distribution along the entire length of the contactor sections. Thetubes or groups of tubes 105, 105A may also be constructed withdifferent, beneficial shape, porosity and permeability characteristicsto enhance gas distribution and liquid film stability along the lengthof the contactor sections.

It should be understood that the foregoing discussion fully describesexamples of components of the various embodiments presented herein, butwhere practical, the individual parts comprising the flow pathways ofthe apparatus may be combined into flow control shapes better suited formanufacturing by casting. Where castings are employed in themanufacturing process, the flow pathways may be created using fewerparts than presented herein.

It should be understood that the alternate embodiments and/or two ormore of the apparatus may be operated in parallel or in series with eachother in the same process train, or in a cascaded, multi-stage processtrain. For example, FIG. 16A shows, schematically, an arrangementwherein a pair of the assemblies A and B are arranged and operated inseries, and a portion of the liquid from the liquid collector vessel 177of apparatus A is introduced into the liquid inlet 153 of the gas-liquidcontactor section 100 of the apparatus B. FIG. 16B shows, schematically,an arrangement wherein a pair of the assemblies A and B are arranged andoperated in parallel, and liquid is introduced into the liquid inlets153 of the gas-liquid contactor sections 100 of apparatus A and Bsimultaneously. It should be understood that, in parallel operation, gasmay also be introduced into the gas inlets 117 of apparatus A and Bsimultaneously.

The longitudinal axis of the tubes 105 and vessel 101 have been shownand described as being oriented vertically with respect to earth'sgravity to more easily comply with industry standard practice for largevessel design, however, it should be understood that the orientation oflongitudinal axis of the tube bundle and vessel may be in anyorientation that is convenient for efficient apparatus design andmanufacturability. The longitudinal axis of the liquid collectionpressure vessel 177 may also be oriented horizontally, as shown in FIG.16B, depending on process requirements, preference and/or on the spaceavailable for a particular application.

Operation

In operation, liquid is introduced tangentially into the inside diameter107 of each tube 105 through liquid inlet nozzle assemblies 119 or 161with sufficient pressure and flow rate to create a high velocity flow ofthe liquid in a thin film 156, as shown schematically in FIG. 7, aroundand along the inner surface of the porous side wall 106 of each tube.When the liquid meets the interior of a tube, the inlet velocity vectormay or may not be divided into a radial velocity component vector and alongitudinal velocity component vector. The longitudinal velocity vectorcomponent may at first introduction of liquid be equal to zero. Theaddition of a longitudinal velocity vector component, if desired, may beaccomplished by controlling the lead angle at which the liquid inletaperture 130 of the liner 126 (FIG. 11A) is disposed tangentiallyrelative to the inside diameter of the tube. Where the direction oflongitudinal flow in the device is approximately in the same directionas earth's gravitational acceleration vector, the lead angle is notparticularly required to achieve the desired flow pattern. The earth'sgravity will naturally induce a longitudinal downward velocity vector tothe liquid film when the tube bundle is arranged vertically and liquidis flowing from top to bottom in the apparatus. The high velocity flowof liquid in a helical pattern around and along the inside walls of thetube produces a centrifugal force of sufficient magnitude, acting toforce the liquid against the inner surface of the tube with a velocityvector direction generally normal or perpendicular to the longitudinalaxis of the tube. The liquid radial velocity, and thus the outwardacceleration, is sufficient to maintain the liquid film against theinner wall surface of the tube throughout its entire length.

Liquid may be introduced into the apparatus using different methodsdepending on the apparatus configuration. In the first embodiment (FIGS.1, 2 and 8), liquid under pressure is introduced through the interior154 of the liquid inlet conduit or pipe 153 into the pressure containingchamber 148 where the liquid flows to all the liquid inlet nozzleassemblies 119 and into all of the porous tubes 105 in the bundlesimultaneously. The bulk liquid flow rate introduced in the single inletpipe 153 is controlled at the overall required capacity and at anadequate pressure ranging from the lowest process design liquid flowrate to the highest process design liquid flow rate, with all tubes inthe bundle supplied at the same flow rate and pressure simultaneously.The bulk process fluid flow control method in this configuration allowsonly one range of process turn-up/turn-down ratio and the wholeapparatus with all tubes in the bundle connected is either on or off.

In the second embodiment (FIGS. 3 and 4), each liquid inlet nozzleassembly 161 has a separate liquid inlet 171 (FIGS. 13A, 13B) to supplyeach porous tube 105 individually, ranging from the lowest design liquidflow rate to the highest design liquid flow rate for one tube of aparticular diameter. The process liquid flow rate may be controlled byindividually feeding each tube or group of tubes such that one or moretubes or group of tubes may be turned off while other tubes or tubegroups are still in operation. Liquid flow control in this configurationallows for sequential ranges or step-wise turn-up/turn-down so thatoverall a much broader range of process turn-down ratio may be achieved.This method may employ tubes of differing diameters and capacities tocover the overall liquid capacity range and turn-down ratio required bythe process.

Pressurized gas is introduced through the inlet 117 (FIG. 4) into thepressure vessel chamber 115 or chambers between the side wall 102 of theouter housing 101 and the outer surfaces of the porous walls 106 of thetubes 105 and forced through the porous walls of the tubes by virtue ofthe differential pressure between the pressurized gas chamber 115 andthe inside diameter 107 of each porous tube. The porous tubes are seatedand sealed at each end in the tube sheets 111 and 113 such that the gascan only flow through the porous walls of the tubes. Where liquid flowcontrol exists for each tube or group of tubes individually in thebundle, the gas supply to the same each tube or group of tubes may beindividually controlled so that gas is not flowing to a tube or tubegroup that is out of service. As shown schematically in FIG. 7, the gaspasses to the inner surface of the porous side wall 106 of the tube 105and is immediately contacted by the liquid 156, which is moving at ahigh velocity relative to the tube wall and to the gas as it enters theinterior of the tube. The gas is sheared from the porous wall by aliquid boundary layer 158 moving approximately perpendicular relative tothe gas. The result of this introduction of gas through the labyrinth ofpores in the porous tubes into a liquid having a centrifugal or outwardacceleration in the approximate opposite direction to the gas velocityvector direction is that a multitude of very tine bubbles 159 areproduced, and are carried away from the tube wall 106 by the movingliquid 156 in its radial flow pattern around the inner surface of eachporous wall 106, and longitudinally toward the liquid exit from eachtube.

The mixture of liquid 156 and gas bubbles 159 forms a two-phase flowthat exists in a helical flow pattern around and along the inner surfaceof each tube. The buoyancy of the bubbles 159 relative to the liquid 156causes them to move toward the region of lowest pressure or the centerzone 107 of the tube and against the centrifugal or outward accelerationof the liquid phase, passing through the froth created by the two phaseflow as it moves around the inner surface of each tube. The gas exitsfrom the two-phase flow at the inner flow boundary 157 created at theinside diameter of the thin film into a gas boundary layer 160 and istransported axially from the tube. It has been observed incountercurrent operation that the gas core 107 rotates in the oppositedirection from the helical liquid flow and as a result, the gas velocityat the gas boundary layer 160 must approach zero and then reversedirection. The effect is like two augers rotating one inside the otherin opposing directions.

Because the specific gravity of the liquid is much higher than thespecific gravity of the gas, the centrifugal or outward accelerationimposes a substantially higher force on the liquid than on the gas. Thegas is thus able to move to the center 107 of the tube 105 while theliquid is forced toward the wall 106 of the tube. The result of thisdensity difference produces a distinct gas phase in and along the axialcore of each porous tube, minimizing liquid entrainment with the gas inthe central portion of the tube, and inducing a clean separation betweenthe gas column at the center of the tube and the two phase flow alongthe inside diameter surface of the tube.

As the bubbles 159 pass through the liquid 156, momentum, heat and massare transferred on a molecular level between the liquid and the gas inaccordance with the laws of thermodynamic equilibrium. Mass transferoccurs between the two components as determined by the value of theappropriate partition coefficient and the initial concentration of thetransferring component in each phase. In general, the concentrations ofthe transferring component in each bubble of gas 159 and in theimmediately surrounding liquid 156 are at or closely approachingequilibrium when the gas in each bubble exits from the gas boundarylayer 160 and bursts into the gas column 107 at the center of the tube.Each volume of gas passes through the liquid only once within theapparatus, and each passage is associated with an approach toequilibrium. Each passage is conceptually related to a McCabe-ThieleMethod theoretical plate.

As a general, and non-limiting example, consider an apparatus within thescope of the invention in which the inside diameter 107 of tube 105 is142 mm (5.59 inches) and has a porous wall thickness of 3.5 mm (0.138inch), and is formed of a commercially available porous media, for thisexample, sintered 316L grade stainless steel having an average pore sizeof 10 microns. It should be understood that the apparatus is modular andscalable. In this example, the starting annular area occupied by theundisturbed liquid film is one-third of the cross-sectional area of tube105 interior cross-sectional area, yielding a liquid film thickness of0.513 inches. The rectangular dimension of the liquid inlet aperture 130or 176 is 0.513 inches in width by 1.443 inches long. The porous tube105 is 19.38 inches long end-to-end between the tube ends 108 and 109and has an effective gas sparging length of 16 inches. There are 4 tubesin the apparatus of the example. Taking 16/1.443 gives about 11 possibleliquid revolutions per tube if a perfect helix is maintained through thesparged length. In practice, the helix lead angle from one revolution ofliquid to the next revolution of liquid decays or becomes largerregardless of tube orientation with respect to earth's gravity. Theactual number of revolutions of liquid is closer to 6 or 8. Fromexperimental work, an example liquid flow rate for this geometry isabout 200 gallons per minute (gpm) per tube or about 800 gpm totalapparatus liquid flow nominal capacity. This flow rate yields a liquidinlet nozzle velocity=q/A, where q=flow rate in ft³/s and A=flow area inft², of 86.7 ft/s, corresponding Reynolds Number for 60° F. water andusing the hydraulic diameter of a rectangular nozzle, of 449,381. Theradial acceleration introduced tangentially into the porous tube 105 ata flow rate of 200 gpm will be 1,002 g or 32,275 ft/s². Also fromexperimental work, this particular flow geometry exhibits liquid filmstability over a usable range from about 125 gpm to about 580 gpm. IfReynolds Number=1×10⁶ is imposed as a limiting design parameter for theliquid inlet nozzle, then this range may be limited to about 445 gpm.The range from 125 gpm to 445 gpm inclusive may or may not yield thedesired process results and depends entirely on the process objective ofinterest. From a purely fluid mechanics point of view, the stable rangeof operation, in this non-limiting example, corresponds to nozzlevelocities from 54 to 193 ft/s, Reynolds Numbers from 280,931 to 1×10⁶,and radial accelerations from 392 g to 4966 g.

To illustrate the tremendous flexibility of the modular design of thepresent invention, consider changing one component, the liquid inletaperture 130 or 176, from a length of 1.443 inches to 1.026 inches orexactly 2 times the film thickness of 0.513 in the above example andkeeping all other geometry and flows the same. The effect from just thisone alteration changes the entire range of operation. For example, if392 g is for some reason determined to be the magical target number forradial acceleration, the corresponding minimum liquid flow rate can nowbe lowered to about 89 gpm with corresponding number of liquidrevolutions now increased to a maximum of 15.5. The net effect in thealtered nozzle is to maintain the same hydrodynamic stability of liquidflow while simultaneously reducing the liquid flow rate and keeping theliquid in contact with a larger volume of gas for a longer time. This isjust one of many parametric scaleable design parameters.

Now consider the gas side of the above example. Going back to the 1000g, 200 gpm example, the gas flow rate, determined experimentally bycorrelation of flow density in scfm (standard cubic feet per minute) perft² of external tube surface area, is about 130. The example isconsidering a 16 inch gas sparging length per tube. The external tubesurface area is 2.05 ft². At a flow density or flux of about 130, thisyields a gas flow rate of about 268 scfm per tube 105 for a total gascapacity of 1072 scfm. Consider that the gas is air. A furthercorrelation discovered by a combination of experimentation andcalculation, suggests that the gas pressure required to balance thecentrifugal acceleration of water trying to escape out of the poroustube is just simply F=ma. Consider 1 square inch of water havingthickness 0.513 inches. The acceleration is 1000 g. The water has aweight density of 62.4 lb/ft³. This calculation yields a force orequivalent gas pressure of 18.52 lb/in². If the gas pressure is 18.52psi, then the volume at actual conditions can be calculated using theideal gas law, p1*v1/t1=p2*v2/t2 where p is pressure, v is volume and tis temperature. The actual gas volume is 268 scfm compressed to 18.52psi or 118.6 acfm (actual cubic feet per minute). 200 gpm/7.48 gallonsper ft³=26.74 ft³/minute of liquid flow.

This result indicates that the example has a volumetric gas to liquidratio of 10 on a standard basis and 4.44 on an actual basis. Thiscorrelation, albeit overly simplistic, agrees very closely withexperimental data measured for four different 10 micron tube diametersand corresponding flow rates. Since the design bases were all similar,the correlation applies to 1000 g operation in a 10 micron tube wherethe liquid occupies ⅓^(rd) of the cross-sectional area of the poroustube. In practice, the gas pressure required to balance the liquid atthe inside boundary of the tube increases slightly with increasingliquid centrifugal acceleration. By extrapolation of experimental flowdata, it is contemplated that the porous tube of the example will flowabout 500 acfm at 50 psig differential measured across the porous media.This high volume gas flow yields gas to liquid ratios of 82 standard and18.7 actual respectively. This differential pressure is published by themanufacturer as the practical limit of the porous media of the example.It is not known at this time if this is a practical limit of operationof the invention or whether this gas flow would blow the liquid film offthe wall of the porous tube. From experience, it appears that if theliquid film has enough centrifugal energy, particularly in a shortsection of tube, it is not possible to disrupt the liquid flow bysparging too much gas to the extent that the rifle barrel flow patterndisintegrates into chaos.

Now consider changing the tube porosity to 15 micron and leaving allother parameters the same. The result of this change will allow more gasflow at a lower differential pressure and produce larger bubbles havingless residence time in the contactor. It is contemplated that realapplications exist where this mode of operation would be practical andwould produce excellent performance.

To complete the mental picture of the example, the exemplary presentcontactor has 4 tubes each having a nominal process capacity of about200 gpm. The turn-down ratio may be about 175 to about 285 gpm withcorresponding gas flows ranging from about 230 to about 400 scfm. Thisgives an overall nominal flow capacity of 800 gpm liquid and about 1000scfm gas. In the first embodiment (FIGS. 1 and 2), the turn-down may bea bulk turn-down 700 to 1140 gpm, or in the second embodiment havingindividually operated tube modules (FIGS. 3 and 4), the turn-down canrange from one tube at 175 gpm to all tubes in service at 1140 gpm.Generally, processes do not require 100% turn-down.

In our example, the contactor section of the vessel has a ⅜″ wallthickness and is 30 inches in diameter with ANSI 150 lb flanges. Themaximum working pressure would be about 200 psig at 200 F. The liquidinlet pressure would be about 75 to 80 psig with gas inlet pressure ofabout 18 to 20 psig. The liquid hold-up volume in liquid collectionvessel 177 is about 1000 gallons with cylinder seam to seam about 8 ftand diameter about 5 feet. The bottom vessel head is a standard ASME 2:1elliptical flanged and dished head. The overall height of the firstembodiment (FIGS. 1 and 2) is about 21′-3″, and the second embodiment(FIGS. 3 and 4) about 18′-10″. The same apparatus configuration can holdup to 5 tubes in the bundle. The tubes 105 can be longer or shorter than16 inches of effective sparging length. The gas supply nozzle, gas exit,liquid inlet and liquid exit of the first embodiment would all be 6″Schedule 40 pipe.

The liquid surface area generated in the example of the apparatus isapproximately 693,000 square feet assuming the maximum number of bubblesat atmospheric pressure using the nominal capacities. This correspondsto a surface area per unit volume of gas-liquid contact generated in 0.9cubic feet of porous tubes of about 770,000 ft²/ft³. Stated another wayfor better visualization, if the liquid having thickness 0.513 inchesand exposed surface 1.443 inches wide was stretched out in a smallchannel on the ground, the distance would need to be about 1091 mileslong to yield the equivalent surface area exposed to air as isillustrated in this example.

The comparison of the above example to the Reynolds Number discussion inthe Background of the Invention for a process capacity of 3000 gpm cannow be made. The example above illustrates the design flexibility andmodular approach of the invention. The scale-up from the examplediscussion of a nominal 200 gpm capacity to 3000 gpm would require 12tubes of this particular diameter operating at 250 gpm each. The vesselcylinder size required to contain 12 tubes is 54″ in diameter. This isless than twice the 30″ diameter needed to house 4 tubes. Alternatively,the scale-up to a 3000 gpm process capacity may be accomplished with afewer number of larger diameter tubes than as presented in the example.The economy of scale of full commercial implementation of this inventionlies in the ability to standardize on perhaps 2 or 3 tube diameters andconsequently 2 or 3 sizes of liners, nozzles, seals, and other customparts that comprise a full assembly. The huge economies available liefurther in the ability to minimize the required pipes, valves, meters,switches, etc., which comprises a full industrial process systemcomplete with automatic operator interface, safety alarms andshut-downs.

It should be understood from the foregoing discussion that the preferredmethod of the present invention performed in the apparatus as disclosedand described, comprises the following general steps:

1. introducing a stream of liquid tangentially to the first end of abundle of porous cylindrical or conical tubes;

2. controlling the flow of a thin film of the liquid in a spiral patternaround and along the inner surface of each porous tube from the firstend to the second end, so as to impose centrifugal or outwardaccelerations within the range of about 2 g to about 8000 g on theliquid at the inner surface of the porous tube;

3. sparging a gas through the wall of each porous tube and through theliquid spiraling through each tube at an overall gas to liquidvolumetric flow ratio of up to the maximum rated differential pressuremeasured across each tube, whereby the overall gas to liquid flow rateis divided into a number of individual transfer units in which theinterfacial contact area between gas and liquid is extremely large,whereby highly efficient transport between liquid and gas is achieved;

4. ceasing sparging of gas into the liquid in a region adjacent to thesecond end of each tube while allowing the liquid to continue spiralingtoward the second end of each tube for a sufficient distance and time toallow degassing of the liquid and separation of the gas and liquid intoan annular film of liquid around the inner circumference of each tubeand a column of gas at the center of each tube;

5. physically dividing liquid from gas at the second end of each tube byinterposing two cylindrical nozzles thus creating an annular nozzlewhere liquid exits the second end and gas is either redirected to thefirst end or allowed to escape from both ends;

6. redirecting the columns of gas back to the first ends of each tube incountercurrent flow relative to the movement of liquid along each tubeor allowing a combination co-current/countercurrent mode of operationwhere gas travels toward the first ends and second ends of each tube;

7. removing the gas from the apparatus through cylindrical nozzles atthe first ends and/or second ends of the apparatus; and

8. removing the liquid from the apparatus.

The apparatus is preferably operated such that liquid does not wet theporous media. If the liquid is clean, then the tubes can be purged anddried adequately to recover from becoming wetted. If the liquid containsparticulate matter, the tubes may become plugged from the inside and gaswill no longer flow through the media. Generally, in practice, the tubesshould be checked and/or replaced on a regular basis. The overall gasflow control system contemplated for use in industrial applications ofthe present invention will incorporate alarms and start-up/shut-downsequences including automatic gas purge and be based on gas flow andacceptable differential pressure across the porous media to protect thetubes from becoming unusable.

Corrosive liquids may be processed using the present method and thecomponents constructed of appropriate materials for the particularapplication, such as exotic metal alloys, plastics, other non-metalliccomponents, compatible sealing elements, linings, coatings, etc. orcombinations thereof. The modular, bolt together form of the apparatusis particularly well suited for utilizing combinations of materials andcomponents selected for the most cost effective implementation of themethod.

For applications requiring very high process pressures, the apparatuscan easily be adapted to use heavier walled steel components, for hightemperatures—thermal insulation, for dangerous materials—double wallcontainment.

The operating parameters of the method of the present invention areselected with the objective of optimizing the overall transportefficiency in the gas-liquid system of interest, generally that of masstransfer, and thus the overall operating efficiency of the apparatus.Widely different objectives may exist with the application of theinvention, and parameters may be developed on a process-by-processbasis. For example, deoxygenation of seawater, requires onlyapproximately a 1:1 up to 4:1 gas to liquid volume ratio (GLR) to stripoxygen out of the seawater. For ozonation, hydrogenation or in general,some chemical processes, the stoichiometric ratios may be very small toaccomplish the objective and only require a GLR of less than 1. For thistype of operation utilizing small GLR, the present apparatus and methodmay utilize short, tight porosity porous tubes to simultaneously satisfythe process requirements and maintain the dynamic requirements of flowand liquid film stability. Where the required process gas volume is toolow to maintain the dynamic requirements, an inert carrier gas can beused with the process gas to increase the overall gas volume supplied tothe invention.

For those processes where gas production and volume throughput aretantamount to successful application of the invention, the system may beconfigured to operate with large gas to liquid volume ratios. In thiscase, the apparatus and method may utilize longer, looser porosityporous tubes in greater number in the bundle to provide enough tubesurface area for the required process gas flow. The porous tube mediamay be segmented to isolate pressure along the length of the porousmedia to achieve uniform gas distribution along the entire length of thecontactor and/or the media may be constructed using a conicalcross-section to improve the uniformity of the gas distribution. If themedia is segmented along its length, each segment may be constructedwith different, beneficial shape, porosity and permeabilitycharacteristics to enhance gas distribution and liquid film stabilityalong the length of the contactor. If the porous media has a conicalcross-section, the porosity and permeability characteristics may beengineered to achieve controlled linear or parabolic gas distributioncharacteristics along the length of the contactor media and/or mediasegments. In the limit, the present apparatus can flow as much gas aswill produce the maximum rated differential pressure measured across theporous media from the gas supply side to the gas exhaust side and isfurther limited by the sonic velocity of compressible gas flowingthrough the porous media and by the sonic velocity of gas exiting thegas exit nozzle assembly and out of the apparatus. Conical cross-sectioncontactor sections in the invention may also be used to increase the gasexit nozzle throat dimension in the limiting case of sonic gas flow.

Depending upon the particular application, liquid is introduced to theapparatus at the lowest possible flow rate to sustain the dynamicrequirements of flow and liquid film stability along the tube length.Where short, tight porosity tubes are employed, the liquid radialacceleration may be very low, say 2 to 10 g. Where longer tubes areemployed, the liquid radial acceleration may exceed the 1500 g designbasis of prior art devices. The overall ratio of gas to liquidvolumetric flow rate expressed at standard temperature and pressureconditions may vary widely from about 1:1 up to the maximum rateddifferential pressure measured across the porous media. Depending on thegas employed, this differential pressure may produce a GLR greater than50:1.

The modular configuration of the present invention allows parameters tobe adjusted for the most efficient operability range including broadturn-up/turn-down ratios that invariably have to be considered andincorporated. The modularity of the present invention allows reductionof studies in process design, mechanical design, and cost accounting todetermine the initial best tube diameter/length ratio versus tube numberto roughly size for the operability range of the process. The processperformance may be fine-tuned by simply adding or subtracting a tubefrom service. Tube porosity and tube length, liquid film thickness, gasoutlet nozzle diameter, etc. can each be changed out in total or inselected contactors in the bundle.

Thus, the present invention has significant differences and advantagesover the prior art, and has the potential to perform a large variety ofindustrial processes very efficiently and economically and further toperform complex multi-component or multi-stage processes includingreactive processes which may not be possible to perform on a large scaleusing other conventional methods. Moreover, a principle advantage of thepresent apparatus is the ability to construct large economic processcapacity completely contained inside relatively simple standardizedpressure/vacuum vessels.

It should be understood that although the apparatus has been presentedprimarily as a gas-liquid contactor it works equally well in certainapplications as a gas-gas contactor or a liquid-liquid contactor. Wherea density gradient exists between two components regardless of phase,the acceleration present in the tube sections causes lighter componentsto separate from heavier components.

While this invention has been described fully and completely withspecial emphasis upon preferred embodiments, it should be understoodthat within the scope of the appended claims the invention may bepracticed otherwise than as specifically described herein.

What is claimed is:
 1. Apparatus for contacting large volumes of gas and liquid across a multitude of microscopic interfaces, comprising: at least one gas-liquid contactor assembly including an outer vessel having a central longitudinal axis circumscribed by a non-porous generally cylindrical side wall with first and second ends, at least one gas inlet for introducing gas into said outer vessel, a plurality of elongate tubes within said outer vessel disposed in circumferential and radially spaced relation having longitudinal axes parallel to said outer vessel longitudinal axis, each of said tubes having a microscopically porous side wall with an inner surface surrounding a hollow interior and opposed first and second ends, first and second seal means engaged in sealing relation with said outer vessel and around said first and second ends of said tubes to form a pressurized gas chamber surrounding said tubes and a gas-liquid separator chamber isolated therefrom by said second seal means, said hollow interior of said tubes being in open fluid communication through said first and second seal means, and said second seal means having a plurality of orifices in coaxial alignment with said seconds ends of said tubes to provide an uninterrupted flow path from said second ends of said tubes; a liquid feed assembly connected with said outer vessel first end and in fluid communication with said first ends of said tubes and having liquid injection means for introducing liquid tangentially into said hollow interior of each of said tubes such that the liquid flows in a thin film in a spiral flow pattern around and along said inner surface of each of said tubes from said first ends to said second ends; a gas-liquid separator assembly in said outer vessel gas-liquid separator chamber including a plurality of target nozzles disposed in coaxial alignment with said seconds ends of said tubes and said orifices in said second seal means, each having a first end spaced relative to said orifices and configured and sized relative thereto to form an annular gas-liquid separator annulus that allows liquid to pass therethrough and redirects gas in a direction countercurrent to the direction of liquid flow above it; a gas exhaust assembly connected with said liquid feed assembly and including at least one gas duct having an interior connected in gas flow communication with said interior of said porous tubes for conducting redirected gas therefrom; and a liquid collection vessel having a first end connected with said outer vessel second end having an interior in fluid communication with said gas-liquid separator chamber and with said second ends of said tubes through said annular gas-liquid separator annulus to receive liquid passing through said annulus.
 2. The apparatus according to claim 1, wherein said first seal means comprises a first disk-shaped tube sheet disposed in sealing relation between said first end of said outer vessel and said liquid feed assembly having a plurality of circumferentially spaced holes extending therethrough; said second seal means comprises a second disk-shaped tube sheet disposed within said outer vessel having an outer periphery engaged in sealing relation with an interior surface of said vessel side wall and having a plurality of circumferentially spaced holes extending therethrough; and said opposed first and second ends of each of said tubes have an exterior surface sealingly engaged in respective said holes in said first and second tube sheets, and an outer facing end of said holes provide an uninterrupted flow path coaxial with said interior of said tubes.
 3. The apparatus according to claim 1, wherein said pressurized gas chamber of said outer vessel is divided into a plurality of segregated pressurized gas chambers each having a gas inlet for introducing gas therein, and each of said elongate tubes are disposed within a respective one of said pressurized gas chambers; whereby each of said elongate tubes may be individually supplied with gas at different pressures.
 4. The apparatus according to claim 1, wherein at least one of said tubes has a hollow interior of a diameter different from the diameter of at least another one of said tubes.
 5. The apparatus according to claim 1, wherein at least one of said tubes has a hollow interior that is tapered along its length between its said opposed first and second ends.
 6. The apparatus according to claim 1, wherein at least one of said tubes has a microscopically porous side wall of different porosity from at least another one of said tubes.
 7. The apparatus according to claim 1, wherein said liquid feed assembly and said gas exhaust assembly comprises a plurality of liquid inlet and gas exhaust nozzles, each having a nozzle housing with generally cylindrical side wall having a reduced diameter exhaust opening at a first end thereof and a larger interior diameter at a second end thereof with a rectangular liquid inlet nozzle aperture through said side wall tangential to its said interior diameter to establish tangential fluid flow of a thin film of incoming liquid; and a vortex finder disposed in said nozzle housing having a central bore through its center coaxial with said exhaust opening to provide a flow path for exhausting return gas, said central bore circumscribed by a generally cylindrical side wall positioned concentrically in said nozzle housing interior diameter in radially inward spaced relation thereto to establish vortex fluid flow of said thin film of incoming liquid, and said vortex finder side wall providing a physical separation between the incoming liquid and the return gas.
 8. The apparatus according to claim 7, wherein said liquid injection nozzle aperture of said nozzles have a cross sectional area sized to produce a thin film of incoming liquid having a thickness in the range of from about 5% to about 28% of the inside diameter of said inner surface of said tubes.
 9. The apparatus according to claim 7, further comprising: a cylindrical erosion resistant liner positioned concentrically in said interior diameter of said nozzle housing and having a cylindrical side wall surrounding an interior diameter with a rectangular liquid inlet aperture extending therethrough tangential to its said interior diameter and aligned in fluid communication with said liquid inlet nozzle aperture to receive liquid therefrom and establish tangential fluid flow of a thin film of the incoming liquid; and said liner interior diameter is spaced radially outward from said vortex finder side wall to establish vortex fluid flow of said thin film of incoming liquid.
 10. The apparatus according to claim 7, further comprising: a generally dome shaped liquid feed and gas exhaust vessel having a first end connected in sealing relation with said outer vessel first end and an enclosed interior divided into a separate liquid chamber at said first end and a gas exhaust chamber at a second end by a divider plate having a central liquid inlet bore and a plurality of circumferentially spaced gas exhaust bores extending therethrough in radially spaced relation thereto; said liquid chamber surrounding said plurality of liquid inlet and gas exhaust nozzles, and each of said plurality of circumferentially spaced gas exhaust bores in said divider plate engaged in sealing relation with a respective said reduced diameter exhaust opening in a respective said nozzle housing; and a liquid inlet conduit having a first end exterior of said vessel extending in sealed relation through said gas exhaust chamber and having a second end connected in fluid communication with said central liquid inlet bore; wherein liquid is introduced through said liquid inlet conduit into said liquid chamber and fed simultaneously to the liquid inlet nozzle aperture in the side wall of the housing of said plurality of liquid inlet and gas exhaust nozzles, and return gas from each of said plurality of tubes is exhausted through each said central bore of said vortex finder, said exhaust bore in said nozzle housing, and through respective said gas exhaust bores in said divider plate into said exhaust gas chamber.
 11. The apparatus according to claim 10, further comprising: a conduit connected in fluid communication between the interior of said liquid collection vessel and the interior of said liquid feed and gas exhaust vessel to equalize gas pressure therebetween.
 12. The apparatus according to claim 7, wherein each said nozzle housing has an outwardly extending liquid inlet conduit in fluid communication with said rectangular liquid inlet nozzle aperture; and liquid is introduced individually to at least one of said plurality of said liquid inlet and gas exhaust nozzles through said liquid inlet conduit and said liquid inlet nozzle aperture in the side wall of said nozzle housing, and return gas is exhausted through said central bore of said vortex finder and said exhaust bore in said nozzle housing; whereby liquid may be introduced into selected ones of said tubes.
 13. The apparatus according to claim 12, wherein liquid is introduced individually to each of said plurality of said liquid inlet and gas exhaust nozzles through said liquid inlet conduit and said liquid inlet nozzle aperture in the side wall of said nozzle housing, and return gas from each of said plurality of tubes is exhausted through each said central bore of said vortex finder and said exhaust bore in said nozzle housing; whereby liquid may be introduced into each or groups of said tubes at different velocities.
 14. The apparatus according to claim 13, wherein said pressurized gas chamber of said outer vessel is divided into a plurality of segregated pressurized gas chambers each having a gas inlet for introducing gas therein, and each of said elongate tubes are disposed within a respective one of said pressurized gas chambers; whereby gas at different pressures may be supplied individually to each or groups of said elongate tubes.
 15. The apparatus according to claim 12, further comprising: a hollow cylindrical erosion resistant liner positioned concentrically within each said liquid inlet conduit.
 16. The apparatus according to claim 1, further comprising: a second gas-liquid contactor assembly disposed between the first stated gas-liquid contactor section and said liquid feed section; said second gas-liquid contactor section including a second outer vessel having a central longitudinal axis circumscribed by a non-porous generally cylindrical side wall with a first end connected with said liquid feed section and a second end connected with said first end of the first stated gas liquid contactor section, at least one gas inlet for introducing gas into said second outer vessel, a second plurality of elongate tubes within said second outer vessel disposed in circumferential and radially spaced relation having longitudinal axes axially aligned with said longitudinal axes of the first stated plurality of tubes, each of said second tubes having a microscopically porous side wall with an inner surface surrounding a hollow interior and opposed first and second ends, third seal means engaged in sealing relation between said first and second outer vessel and around said first and second ends of said first and second plurality of tubes to form a second pressurized gas chamber surrounding said second plurality of tubes, said hollow interior of said first and second plurality of tubes being in open fluid communication through said third seal means; whereby gas at different pressures may be supplied individually to said first and said second plurality of tubes.
 17. The apparatus according to claim 1, wherein each of said tubes has a microscopically porous side wall of sufficient porosity to produce up to about 50 psig differential gas pressure measured across the porous media.
 18. The apparatus according to claim 1, wherein said microscopically porous side wall of each of said tubes contains a surface active catalytic material in proximity to its said inner surface.
 19. The apparatus according to claim 1, wherein said inner surface of each of said tubes is surface treated to enhance fluid flow characteristics.
 20. The apparatus according to claim 1, further comprising: gas baffle means in said pressurized chamber of said outer vessel to inhibit the incoming gas stream from impinging directly on the exterior surface of said tubes and facilitate even gas distribution along the exterior surfaces thereof.
 21. The apparatus according to claim 1, further comprising: liquid motion baffle means in said liquid collection vessel to mitigate sloshing.
 22. The apparatus according to claim 1, further comprising: heating means in said liquid collection vessel for heating liquid contained therein.
 23. The apparatus according to claim 1, wherein said porous side wall of at least one of said tubes is connected with an electrical source to function as a resistance heating element.
 24. The apparatus according to claim 1, further comprising: an ultraviolet emitting light source disposed inside and along the central axis of at least one of said porous tubes.
 25. The apparatus according to claim 1, wherein said gas exhaust assembly contains a gas scrubber section near the exit of the gas after it has been in contact with the liquid to scrub out entrained liquid from the gas prior to exiting the vessel, and means for returning the scrubbed out liquid to said liquid collection vessel.
 26. The apparatus according to claim 1, wherein said gas-liquid separator assembly includes sensor means for monitoring the gas-liquid flow pattern in said gas-liquid contactor section.
 27. The apparatus according to claim 1, further comprising: filter means disposed between said gas inlet and said porous side wall of said tubes for filtering gas introduced into said outer vessel.
 28. The apparatus according to claim 1, wherein said target nozzles of said gas-liquid separator assembly are spaced relative to said orifices and configured and sized relative thereto to form an annular gas-liquid separator annulus that allows liquid to pass therethrough and redirects gas in a direction countercurrent and co-current to the direction of liquid flow above allowing the gas to travel toward either of said first ends and second ends of each of said tubes.
 29. The apparatus according to claim 1, wherein said liquid collection vessel has a liquid outlet connected in fluid communication with a said liquid inlet of a liquid feed assembly of a second apparatus as recited in claim 1 for introducing gas thereto; whereby a first and a second said apparatus are operated in series.
 30. The apparatus according to claim 1, wherein said liquid inlet of said liquid feed assembly is connected in parallel with a said liquid inlet of a said liquid feed assembly of a second apparatus as recited in claim 1 and both are joined to a common liquid supply source; and said gas inlet of said gas-liquid contactor assembly is connected in parallel with a said gas inlet of a gas-liquid contactor assembly of a second apparatus as recited in claim 1 and both are joined to a common gas supply source; whereby a first and a second said apparatus are operated in parallel. 